1. Field of the Invention
This invention is concerned with the breaking or resolution of oil-in-water (O/W) bituminous emulsions by treatment with salts of polymers and/or co-polymers.
2. Description of the Prior Art
A great volume of hydrocarbons exist in known deposits of tar sands. These deposits occur at various places, the Athabasca tar sands in Canada being an example. The petroleum in a tar sand deposit is an asphaltic bitumen of a highly viscous nature ranging from a liquid to a semi-solid. These bituminous hydrocarbons are usually characterized by being very viscous or even non-flowable under reservoir conditions by the application of driving fluid pressure.
Where surface mining is not feasible, the bitumen must be recovered by rendering the tar material mobile in-situ and producing it through a well penetrating the tar sand deposit. These in-situ methods of recovery include thermal, both steam and in-situ combustion and solvent techniques. Where steam or hot water methods are used, a problem results which aggravates the recovery of the bitumen. The difficulty encountered is emulsions produced by the in-situ operations. These emulsions are highly stable O/W emulsions which are made even more stable by the usual presence of clays. Most liquid petroleum emulsions are water-in-oil (W/O) types. These normal W/O emulsions are broken by methods known in the art. However, the bitumen emulsions which are O/W types present a much different problem, and the same demulsifiers used in W/O emulsions will not resolve the O/W bitumen emulsions. The uniqueness of these O/W bitumen emulsions is described in C. W. W. Gewers, J. Canad. Petrol. Tech., 7(2), 85-90 (1968). (Prior art Reference A.) There is much prior art concerning the resolution of normal W/O emulsions. Some of the art even mistakenly equates bitumen O/W emulsions with these W/O emulsions. The following is a list of several art references.
B. U.S. Pat. No. 4,238,230 discloses the breaking of an O/W emulsion by adding to the emulsion a cationic polyacrylamide. This patent discloses and claims using polymers and co-polymers of monomers disclosed herein but not neutralized to make the salt. Our invention makes clear that in order to break bitumen emulsions which are not addressed in the patent the polymers and co-polymers of the cationic polyacrylamides must be converted to the salt form, and in the case of co-polymers comprise the majority of the polymer. The patent only breaks conventional O/W emulsions (not bitumen emulsions) and uses the polymers without conversion to salt forms. Also, the patent discloses that as the percentage of the cationic polyacrylamide portion of the co-polymer declines, the effectiveness of the demulsification increases. Surprisingly, we have found that the cationic polyacrylamides, whether in homopolymer or co-polymer form, must be neutralized to the salt form before they are effective on bitumen emulsions and must be the majority component in any co-polymer in order to be effective bitumen emulsion breakers.
C. U.S. Pat. Nos. 4,141,854 and 4,154,698 disclose the cationic polyacrylamides encompassed by our invention as co-polymers wherein the cationic polyacrylamides comprise less than 50% of the copolymer and are not in the salt form to break standard (not bitumen) W/O or O/W emulsions. We have found that these emulsion breakers are ineffective in breaking bitumen emulsions.
D. U.S. Pat. No. 3,316,181 discloses the use of diallyl dimethylamine co-polymers for breaking O/W emulsions.
E. U.S. Pat. No. 3,171,805 discloses flocculating solids from sewage containing anionic surfactants by using homo- or co-polymers of cationic polyacrylamides.
F. U.S. Pat. No. 3,487,003 discloses separating middlings from tar sand mining streams by treating with a flocculant which includes cationic polyacrylamides.
We have found that the use of particular co-polymers or homopolymers of certain cationic polyacrylamides, when used in the acid form and when comprising the majority of any co-polymer, are effective in breaking bitumen emulsions.